Brother LX-300 Service Manual page 157

Problem
b. Defective LED Low output from the main
on the Switch CPU ports P30 (Pin 73),
PCB P33 (Pin 76), P34 (Pin 77),
and P52 (Pin 27) that drive
indicators LED1 to LED4?
Does LED1 to LED4 light
when Pin 1, Pin 9 to Pin 11
on Main PCB connector
CN16 is Low?
Check Item
Defective main
CPU#3.
Defective switch
harness assy.
Defective LED1 to
LED4.
Cause Remedy
Replace Main PCB
assy.
Replace switch
harness assy.
Replace the Switch
PCB.
7-7
See
Repair
Section
Replace 3.3.3
CPU#3. 3.3.4
3.3.5
3.5.1
3.3.3
3.3.4
3.3.5
3.5.3
Replace 3.3.3
indicator 3.3.4
LED1 to 3.3.5
LED4. 3.3.7
3.3.8
3.3.9
3.3.10
3.5.3